OBJECTIVES: l. To identify the lesions temperature sensitive (ts) mutants of vesicular stomatitis virus (VSV) from complementation groups III and V, specifically the protein species which is changed, the amino acid change(s) involved, and alterations in peptide fingerprints; 2. To correlate these changes with temperature dependent alterations in the physical state of the viral membrane as measured by lipid composition, electron microscope observations, spin labelling and fluorescence properties of the virion; 3. To reconstitute the purified mutant proteins with lipids and demonstrate temperature-dependent properties of the reconstituted lipid-protein system similar to that seen in the intact virion. This will elucidate some of the chemical interactions between viral membrane protein and lipid, and will provide insight into the forces responsible for viral assembly, and for viral stabilization of the mature virion.